1. Field of the Invention
The invention relates to a method of processing waste materials containing noxious metals.
Waste materials of this type are for instance fly ash, gypsum, soil contaminated with heavy metals, sludge, dredged harbour sludge, sludge obtained from sewage treatment, jarosite obtained in the preparation of zinc, cadmium containing pigments in waste materials and similar materials.
2. Description of the Prior Art
Processing such noxious metal containing waste materials causes many problems as the noxious metals are easily leached from such waste materials during storage and this will involve contamination of the surrounding and contamination of the ground water respectively.
Thus, from an environmental point of view very severe requirements have to be met in order to be allowed to store and to process such waste materials.
A well known example of a waste material containing noxious anionic metals is dredged harbour sludge which has to be stored in particularly prescribed areas.
Another waste material to be processed involving much problems is fly ash emitted by coal driven electrical plants. This fly ash contains many noxious metals and though it has been tried to convert fly ash into particles from which noxious metals cannot be leached, the still increasing amounts of fly ash to be processed give rise to contamination of the environment due to leaching of noxious metals during storage in the open air.